R-3c–Pbnm phase transition of La1−xSmxGaO3 (0<x<0.3) perovskites and crystal structures of the orthorhombic and trigonal phases

The first-order phase transition in La1−xSmxGaO3 solid solution perovskite as well as crystal structures of both, room- (RT) and high-temperature (HT) phases, have been studied by means of powder diffraction technique using synchrotron radiation, DTA and DSC analyses. The RT structure of mixed crystals with x=0.10, 0.17 and 0.30 belong to the orthorhombically distorted GdFeO3 structure type (Pbnm space group, Z=4), whereas the symmetry of HT La0.9Sm0.1GaO3 phase is rhombohedral (R-3c space group, Z=6). Transition temperature Tc from the orthorhombic to the rhombohedral structure is linearly related to x following Tc=422(5)+2599(29)x as a first approximation.